This invention relates generally to apparatus and methods for acquiring data related to one or more detected characteristics and more particularly, but not by way of limitation, to apparatus and methods for locally monitoring a plurality of conditions of a process near the process and for making the data corresponding to the conditions available to a location remote from the process.
To accurately control a process, several conditions or characteristics existing throughout the process need to be monitored so that one knows whether the process is being performed as it should be. For example, during a cementing operation at an oil or gas well site, a cement slurry is produced and pumped into the well. To monitor the quality of the slurry and its placement in the well, various pressures, flow rates and densities associated with the slurry and its flow need to be known. Such a process is carried out over a considerable physical area of the well site, and the conditions or characteristics to be known exist at various spaced locations throughout the process area, so that human observation of locally disposed gauges or readouts would not alone provide satisfactory monitoring of the job. Therefore, there is the need for an automated monitoring system and method by which data representing conditions or characteristics to be monitored can be collected and centrally observed so that more accurate control of the process can be achieved.
This general need has been recognized, and we are aware of two systems which have been proposed particularly for use in monitoring characteristics associated with a cementing job at a well site. The PACR system of Dowell Schlumberger monitors pressure, flow rate and density and provides a graphic display and magnetic tape recording. In this system, each sensor for detecting the respective characteristics requires individual cabling to be run directly to the central recording unit. Furthermore, this system is limited to monitoring three density, three pressure and six flow rate characteristics. Additional characteristics can be monitored, but this requires a complete duplicate PACR system. Another system, the PDR system of Halliburton Company (the assignee of the present invention) has limitations similar to the PACR system.
Although the PACR and PDR systems provide automated monitoring of a number of characteristics associated with a process, they have relatively limited capacities before entire duplicate systems need to be used. Furthermore, if such duplicate systems are used, then there is no one central recording station compiling all the monitored information.
Another shortcoming of the PACR and PDR systems is that they require individual conductors from each transducer or detector to be run to the central recording unit. This is relatively expensive in that such runs of cabling can be long. Such multiple conductors require additional maintenance and can create hazardous situations to personnel when they are strung throughout the well site.
A further limitation is that the PACR and PDR systems are not readily adaptable for accommodating dispersed locations where conditions or characteristics are to be monitored as well as where equipment is to be subsequently controlled to change the conditions or characteristics. That is, these systems are primarily, if not exclusively, unitized data acquisition systems to which multiple cables are run for conveying the monitored signals. They do not include modularized components which can be dispersed throughout a process area for both monitoring conditions and controlling the process.
Therefore, there is the need for an apparatus and an associated method which can be used at dispersed locations throughout a process area for retrieving data to be used in monitoring the process and for applying control signals, such as to change the monitored conditions or characteristics.